The present invention relates generally to semiconductor packaging, and more particularly to an improved semiconductor package that has reduced susceptibility to cracking and a method of making the package.
As is well known, integrated circuits are formed on semiconductor dies. Such circuits are formed with multiple layers of materials, e.g., conductors and insulators that interconnect tiny transistors. The dies can be fragile and so must be protected. Further, because the dies are so small, they often are attached to a substrate that is used to interconnect the circuit formed in the die to other circuits. For example, the dies are susceptible to cracking especially at the corners caused by handling and pick-and-place machinery.
Referring now to FIG. 1, a partially packaged semiconductor device 10 is shown. The device 10 includes a semiconductor die 12 attached and electrically connected to a multi-layer wiring substrate 14. One way of attaching and electrically connecting the die 12 to the substrate 14 is with solder balls (not shown) attached to an underside of the die 12. The solder balls interconnect conductive terminals of the die 12 with the wiring pattern formed in the substrate 14. An underfill material 16 like epoxy is disposed in a gap between the die 12 and the substrate 14.
As discussed above, it is important that the die 12 is protected from damage during handling. One way to test the package integrity is to drop a weight 18 having a tip 20 on a corner of the die 12 to test the susceptibility of the die 12 to cracking.
Referring now to FIG. 2, an enlarged view of a portion of the die 12 and the underfill material 16 is shown. The underfill material 16 reaches to about half of the height of the die 12. For example, if the die 12 has a height of about 25 mils then the underfill material 16 has a height of about 12.5 mils. When the weight 18 is dropped onto the corner of the die 12, cracks are formed in an area 22 in the die 12. For the case where the underfill material 16 reaches to about half the height of the die 12, the cracks may extend to a depth of about 10.5 mils.
FIG. 3 shows a die 24 having underfill material 26 that extends about two-thirds up the side of the die 24. In this case, when the weight 18 is dropped onto the die 24, cracks have been measured to a depth of about 8.0 mils. That is, for a die having a height of 25.0 mils and the underfill material having a height of 16-17 mils, then the cracks indicated at cracking area 26 may extend to a depth of about 8.0 mils. Thus, although the depths of the cracks have been reduced, there is still room for improvement.
It would be advantageous to have a packaged device in which the risk of the die cracking was substantially reduced or eliminated.